 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.runtime;

 import org.eclipse.core.runtime.CoreException;

 /**
  * A configuration element, with its attributes and children,
  * directly reflects the content and structure of the extension section
  * within the declaring plug-in's manifest (<code>plugin.xml</code>) file.
  * <p>
  * This interface also provides a way to create executable extension
  * objects.
  * </p>
  * <p>
  * These registry objects are intended for relatively short-term use. Clients that
  * deal with these objects must be aware that they may become invalid if the
  * declaring plug-in is updated or uninstalled. If this happens, all methods except
  * {@link #isValid()} will throw {@link InvalidRegistryObjectException}.
  * For configuration element objects, the most common case is code in a plug-in dealing
  * with extensions contributed to one of the extension points it declares.
  * Code in a plug-in that has declared that it is not dynamic aware (or not
  * declared anything) can safely ignore this issue, since the registry
  * would not be modified while it is active. However, code in a plug-in that
  * declares that it is dynamic aware must be careful when accessing the extension
  * and configuration element objects because they become invalid if the contributing
  * plug-in is removed. Similarly, tools that analyze or display the extension registry
  * are vulnerable. Client code can pre-test for invalid objects by calling {@link #isValid()},
  * which never throws this exception. However, pre-tests are usually not sufficient
  * because of the possibility of the extension or configuration element object becoming
  * invalid as a result of a concurrent activity. At-risk clients must treat
  * <code>InvalidRegistryObjectException</code> as if it were a checked exception.
  * Also, such clients should probably register a listener with the extension registry
  * so that they receive notification of any changes to the registry.
  * </p><p>
  * This interface can be used without OSGi running.
  * </p><p>
  * This interface is not intended to be implemented by clients.
  * </p>
  */
 public interface IConfigurationElement {
     /**
      * Creates and returns a new instance of the executable extension
      * identified by the named attribute of this configuration element.
      * The named attribute value must contain a fully qualified name
      * of a Java class. The class can either refer to a class implementing
      * the executable extension or to a factory capable of returning the
      * executable extension.
      * <p>
      * The specified class is instantiated using its 0-argument public constructor.
      * <p>
      * Then the following checks are done:<br>
      * If the specified class implements the {@link IExecutableExtension}
      * interface, the method {@link IExecutableExtension#setInitializationData(IConfigurationElement, String, Object)}
      * is called, passing to the object the configuration information that was used to create it.
      * <p>
      * If the specified class implements {@link IExecutableExtensionFactory}
      * interface, the method {@link IExecutableExtensionFactory#create()}
      * is invoked.
      * </p>
      * <p>
      * Unlike other methods on this object, invoking this method may activate
      * the plug-in.
      * </p>
      *
      * @param propertyName the name of the property
      * @return the executable instance
      * @exception CoreException if an instance of the executable extension
      * could not be created for any reason
      * @see IExecutableExtension#setInitializationData(IConfigurationElement, String, Object)
      * @see IExecutableExtensionFactory
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      */
     public Object createExecutableExtension(String propertyName) throws CoreException;

     /**
      * Returns the named attribute of this configuration element, or
      * <code>null</code> if none.
      * <p>
      * The names of configuration element attributes
      * are the same as the attribute names of the corresponding XML element.
      * For example, the configuration markup
      * <pre>
      * &lt;bg pattern="stripes"/&gt;
      * </pre>
      * corresponds to a configuration element named <code>"bg"</code>
      * with an attribute named <code>"pattern"</code>
      * with attribute value <code>"stripes"</code>.
      * </p>
      * <p> Note that any translation specified in the plug-in manifest
      * file is automatically applied.
      * </p>
      *
      * @param name the name of the attribute
      * @return attribute value, or <code>null</code> if none
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      */
     public String getAttribute(String name) throws InvalidRegistryObjectException;

     /**
      * Returns the named attribute of this configuration element, or
      * <code>null</code> if none.
      * <p>
      * The names of configuration element attributes
      * are the same as the attribute names of the corresponding XML element.
      * For example, the configuration markup
      * <pre>
      * &lt;bg pattern="stripes"/&gt;
      * </pre>
      * corresponds to a configuration element named <code>"bg"</code>
      * with an attribute named <code>"pattern"</code>
      * with attribute value <code>"stripes"</code>.
      * </p>
      * <p>
      * Note that any translation specified in the plug-in manifest
      * file for this attribute is <b>not</b> automatically applied.
      * </p>
      *
      * @param name the name of the attribute
      * @return attribute value, or <code>null</code> if none
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      * @deprecated The method is equivalent to the {@link #getAttribute(String)}. Contrary to its description,
      * this method returns a translated value. Use the {@link #getAttribute(String)} method instead.
      */
     public String getAttributeAsIs(String name) throws InvalidRegistryObjectException;

     /**
      * Returns the names of the attributes of this configuration element.
      * Returns an empty array if this configuration element has no attributes.
      * <p>
      * The names of configuration element attributes
      * are the same as the attribute names of the corresponding XML element.
      * For example, the configuration markup
      * <pre>
      * &lt;bg color="blue" pattern="stripes"/&gt;
      * </pre>
      * corresponds to a configuration element named <code>"bg"</code>
      * with attributes named <code>"color"</code>
      * and <code>"pattern"</code>.
      * </p>
      *
      * @return the names of the attributes
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      */
     public String [] getAttributeNames() throws InvalidRegistryObjectException;

     /**
      * Returns all configuration elements that are children of this
      * configuration element.
      * Returns an empty array if this configuration element has no children.
      * <p>
      * Each child corresponds to a nested
      * XML element in the configuration markup.
      * For example, the configuration markup
      * <pre>
      * &lt;view&gt;
      * &nbsp&nbsp&nbsp&nbsp&lt;verticalHint&gt;top&lt;/verticalHint&gt;
      * &nbsp&nbsp&nbsp&nbsp&lt;horizontalHint&gt;left&lt;/horizontalHint&gt;
      * &lt;/view&gt;
      * </pre>
      * corresponds to a configuration element, named <code>"view"</code>,
      * with two children.
      * </p>
      *
      * @return the child configuration elements
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      * @see #getChildren(String)
      */
     public IConfigurationElement[] getChildren() throws InvalidRegistryObjectException;

     /**
      * Returns all child configuration elements with the given name.
      * Returns an empty array if this configuration element has no children
      * with the given name.
      *
      * @param name the name of the child configuration element
      * @return the child configuration elements with that name
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      * @see #getChildren()
      */
     public IConfigurationElement[] getChildren(String name) throws InvalidRegistryObjectException;

     /**
      * Returns the extension that declares this configuration element.
      *
      * @return the extension
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      */
     public IExtension getDeclaringExtension() throws InvalidRegistryObjectException;

     /**
      * Returns the name of this configuration element.
      * The name of a configuration element is the same as
      * the XML tag of the corresponding XML element.
      * For example, the configuration markup
      * <pre>
      * &lt;wizard name="Create Project"/&gt;
      * </pre>
      * corresponds to a configuration element named <code>"wizard"</code>.
      *
      * @return the name of this configuration element
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      */
     public String getName() throws InvalidRegistryObjectException;

     /**
      * Returns the element which contains this element. If this element
      * is an immediate child of an extension, the
      * returned value can be downcast to <code>IExtension</code>.
      * Otherwise the returned value can be downcast to
      * <code>IConfigurationElement</code>.
      *
      * @return the parent of this configuration element
      * or <code>null</code>
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      * @since 3.0
      */
     public Object getParent() throws InvalidRegistryObjectException;

     /**
      * Returns the text value of this configuration element.
      * For example, the configuration markup
      * <pre>
      * &lt;script lang="javascript"&gt;.\scripts\cp.js&lt;/script&gt;
      * </pre>
      * corresponds to a configuration element <code>"script"</code>
      * with value <code>".\scripts\cp.js"</code>.
      * <p> Values may span multiple lines (i.e., contain carriage returns
      * and/or line feeds).
      * <p> Note that any translation specified in the plug-in manifest
      * file is automatically applied.
      * </p>
      *
      * @return the text value of this configuration element or <code>null</code>
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      */
     public String getValue() throws InvalidRegistryObjectException;

     /**
      * Returns the untranslated text value of this configuration element.
      * For example, the configuration markup
      * <pre>
      * &lt;script lang="javascript"&gt;.\scripts\cp.js&lt;/script&gt;
      * </pre>
      * corresponds to a configuration element <code>"script"</code>
      * with value <code>".\scripts\cp.js"</code>.
      * <p> Values may span multiple lines (i.e., contain carriage returns
      * and/or line feeds).
      * <p>
      * Note that translation specified in the plug-in manifest
      * file is <b>not</b> automatically applied.
      * For example, the configuration markup
      * <pre>
      * &lt;tooltip&gt;#hattip&lt;/tooltip&gt;
      * </pre>
      * corresponds to a configuration element, named <code>"tooltip"</code>,
      * with value <code>"#hattip"</code>.
      * </p>
      *
      * @return the untranslated text value of this configuration element or <code>null</code>
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      * @deprecated The method is equivalent to the {@link #getValue()}. Contrary to its description,
      * this method returns a translated value. Use the {@link #getValue()} method instead.
      */
     public String getValueAsIs() throws InvalidRegistryObjectException;

     /**
      * Returns the namespace for this configuration element. This value can be used
      * in various global facilities to discover this configuration element's contributor.
      *
      * @return the namespace for this configuration element
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      * @see IExtensionRegistry
      * @since 3.1
      * @deprecated As namespace is no longer restricted to the contributor name,
      * use {@link #getNamespaceIdentifier()} to obtain namespace name or {@link #getContributor()}
      * to get the name of the contributor of this registry element.
      * <p>
      * In the past namespace was dictated by the name of the bundle. If bundle <code>org.abc</code>
      * contributed registry element with Id of <code>MyId</code>, the namespace of
      * the element was always set to <code>org.abc</code>, producing the qualified name of
      * <code>org.abc.MyId</code>.
      * </p><p>
      * The namespace used to be the same as the bundle name. As a result, the {@link #getNamespace()}
      * method was used both to obtain the name of the bundle and to obtain the namespace of a registry
      * element.
      * </p><p>
      * Since 3.2, the extension registry allows elements to specify qualified name. The extension point
      * of the plug-in <code>org.abc</code> could specify <code>org.zzz.MyExtPoint</code> as
      * an Id. In this case, namespace name is <code>org.zzz</code>, but the contributor
      * name is <code>org.abc</code>.
      * </p><p>
      * (The use of a simple Id is still a preferred way. Whenever possible, specify only the simple
      * Id and let runtime take care of the rest.)
      * </p><p>
      * If your code used the {@link #getNamespace()} to obtain the name of the contributing bundle,
      * use {@link #getContributor()}. The typical usage pattern here is to find a bundle name to obtain
      * some information from the corresponding OSGi bundle. For example, deducing the file location
      * specified as a relative path to the bundle install location would fall into this group.
      * </p><p>
      * If your code used the {@link #getNamespace()} to obtain the namespace of the registry element,
      * use {@link #getNamespaceIdentifier()}. Typically, this is the case when code is trying to process
      * registry elements belonging to some logical group. For example, processing notifications for all
      * elements belonging to the <code>org.abc</code> namespace would fall into this category.
      * </p>
      */
     public String getNamespace() throws InvalidRegistryObjectException;

     /**
      * Returns the namespace name for this configuration element.
      *
      * @return the namespace name for this configuration element
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      * @since org.eclipse.equinox.registry 3.2
      */
     public String getNamespaceIdentifier() throws InvalidRegistryObjectException;

     /**
      * Returns the contributor of this configuration element.
      *
      * @return the contributor for this configuration element
      * @throws InvalidRegistryObjectException if this configuration element is no longer valid
      * @since org.eclipse.equinox.registry 3.2
      */
     public IContributor getContributor() throws InvalidRegistryObjectException;

     /* (non-javadoc)
      * @see Object#equals(java.lang.Object)
      */
     public boolean equals(Object o);

     /**
      * Returns whether this configuration element object is valid.
      *
      * @return <code>true</code> if the object is valid, and <code>false</code>
      * if it is no longer valid
      * @since 3.1
      */
     public boolean isValid();
 }

